Chang'e 2: China's Lunar Mapper that visited an asteroid.

Mockup of Chang'e 2 at the Bejing Air and Space Museum. Credit: Shujianyang CC BY-SA 4.0

• Launch Date: October 1, 2010
• Launch Site: Launch Complex 2, Xichang, China
• Launch Vehicle: Long March (Chang Zheng) 3C
• Mission Type: Orbiter/flyby
• Targets: Moon & Toutatis
• Dimensions: N/A
• Mass: 2480 Kilograms

In 2010, China launched their Chang'e 2 spacecraft. The goal of the mission was to map the surface of the Moon, in preperation for the landing of Chang'e 3 and the Yutu rover. After this, the spacecraft made a flyby of the asteroid Toutatis.

The Mission

Chang'e 2 was intended as a backup to Chang'e 1. Chang'e 1 was launched in 2007, and completed its mission with flying colours. With this success under their belt, the China National Space Administration (CNSA) improved the instruments on Chang'e 2, and gave it more mission goals. 

After launch, Chang'e 2 only needed to perform one course correction to reach the Moon, because of it's high level of accuracy. The spacecraft entered Lunar orbit on October 6, with an attitude of around 100 kilometres. The spacecraft would later lower it's perilune (lowest point in lunar orbit) to 15 kilometres. On April 1, 2012, Chang'e 2 ended it's primary lunar mapping mission.

After successfully mapping the lunar surface at a high resolution, the probe was moved to the L2 Lagrange point, in order to test deep space communication. It entered orbit around L2 on August 25, 2011.

On April 15, 2012, the spacecraft prematurely left the L2 point in order to visit asteroid Toutatis as it made a close flyby of Earth. On December 13, 2013, Chang'e 2 made a successful flyby of the asteroid, with closest approach being around 3.2 Kilometres. Because of a high relative velocity (10.73 Kilometres per second) Chang'e 2 could only take high resolution images for a short period of time.

Map of boulders on Toutatis. Credit: CNSA/Nature/Yun Jiang, Jianghui Ji, Jiangchuan Huang, Simone Marchi, Yuan Li, and Wing-Huen Ip

After the flyby, China continued to communicate with the spacecraft until 2014. China announced that the spacecraft became the "smallest man-made asteroid in the solar system," which is untrue, as some of NASA's Pioneer spacecraft and space debris is smaller than Chang'e 2.

The Targets

LROC WAC mosaic of the Moon's near side. Credit: NASA/GSFC/Arizona State University

• Date Discovered: Known To The Ancients
• Radius: 1737.5 Kilometres
• Mass: 7.347673092x10^22 Kilograms
• Density: 3.344 g/cm^3
• Rotational Period: 27.3 Days
• Orbital Period: 27.3 Days

Chang'e 2 mosaic of Toutatis. Credit: CNSA/Yun Jiang, Jianghui Ji, Jiangchuan Huang, Simone Marchi, Yuan Li, and Wing-Huen Ip CC BY 4.0

• Date Discovered: January 4, 1989
• Designation: 4179 Toutatis (1989 AC)
• Class: Apollo [NEO]
• Radius: 2.7 Kilometres
• Rotational Period: 176 Hours
• Orbital Period: 1482.22 Days (4.06 Years)